Lapping machine



Jan. 29, 1957 Filed Nov. 24, 1952 5. A. BOETTCHER ET AL LAPPING MACHINE2 Sheets-Sheet l INVENTORS.

STE HENAIBOETTCHER BY HAROLD w. GOULD Jan. 29, 1957 Filed Nov. 24, 1952s. A. BOETTCHER ET AL 2,779,139

LAPPING MACHINE 2 Sheets-Sheet 2 A INVENTORS:

W STEPHEN ABOETTCHER a. X HAROLD w. GOULD BY fdwawd R, 52mm.)

United States Patent LAPPING MACHINE Stephen A. Boettcher and HaroldW;Gould, Evanston, Ill., assignors to Crane Packing ,Company, Chicago,Ill., a corporation of Illinois Application November 24, 1952,- SerialNo. 322,182 1 12 Claims. (Cl. '51-13"1) The present invention relates toalapping machine.

fixture or work holder designed for -use:-in connection August 28, 1951,for Lapping-Ma'chine.

without modification, be employed in connection with other types oflapping machines-having associated there with a lap surface which ismovable in its own plane to Y produce the necessary lapping operations;

This invention is designed as an improvement over'the lapping machinefixture shown and described in the copending application of Stephen A.Boettche r, Serial No.- 282,96( filed April 18, 1952', for a Methodof'and-App'aratus for Lapping Articles, now PatentNo. 2,722,089 datedNovember. 1, 1955. In this application-just referred to, there has beenshown and described a method of and apparatus for producing fiatsurfaces on'articles by a lapping operation wherein the plane of thefinishedlapped face on the article assumes a definite and predeterminedangularity within very fine limits with respect to the plane of someother face on the article or to a fixed reference plane establishedrelative to the-article itself. According to the method and apparatusemployed in this application, there is provided an article holder orfixture to which an article such as a thin piezoelectric crystal may befixedly secured and by means of which it may be applied to the lapsurface for lapping purposes with the weight of the fixture resting uponthe article to maintain the latter in contact with the lap surface.During lapping, the article holder is moved toward the lapped surface ata rate commensurate with the speed of lapping. The article holder isprovided with a fixed non-wearing three point suspension for the holderon the lap surface in such a manner that continued lapping of the faceof the article will bring the individual points of suspension intocoincidence with the plane of the lap surface. Since the three points ofsuspension are of a non-wearing nature, movement of the suspensionpoints into such coincidence with the plane of the lap surface willrelieve the pressure of the article on the lap surface and substantiallyterminate further lapping operations. The improved fiXture comprisingthe present invention embodies the same general principles. as thefixture shown in the application of Boettcher but it constitutes 'animprovement thereover in that novel means are provided for efiectinginitial adjustment of the suspension points relative to the body of thefixture with the adjustment being carried out within very fine limits sothat the fixed reference plane which forms a basis for the lappingoperations may be accurately established prior to the commencement oflapping operations.

It is, therefore, among the principal objects of the present inventionto provide a lapping fixture or article holder of the type shown in theapplication of Boettcher, to-

gether with novel means for adjusting the positions'of the suspensionpoints associated with the fixture in such 1.

2,779,139 Patented Jan. 29, 1957 2 I a manner that an extremely fineadjustment involving very small displacements of the suspension pointsis attained.

Astill further object of the inventionis to provide a fixture of thischaracter in which the adjustment of the individual suspension pointsmay be made by rotation of adjustment screw and in whicha fairly largeincrement of turning movement of the adjustment screw will result in anextremely small component of linear displacement in a desiredverticaldirection of-the individual suspension point.

In carrying out this last mentioned object, the invention contemplatesthe provision of a pivoted or swingable support for the suspension pointtogether with means for adjustably tilting or swinging the support aboutan axis. The suspension point is mounted on the tiltable support at aregion remotefrom its tilting axis so that when the support is tiltedabout its axis the suspension point will be" moved in 'an arcuate pathhaving both horizontal and vertical components of motion. The horizontalcomponent of motion through which the suspension point moves is afunction of the sine of the angle of tilting of the support and,although its absolute movement is small, its differential. rate ofincrease is comparatively large. Thevertical component of movement ofthe suspension point is a function of the cosine of the angle of tiltingmovement of the support and its difierential rate of increase istherefore extremely small. Tilting movement ot the support is efiectedby an adjustment screw of relatively fine pitch so that each turn of thescrew will effect but a small angular displacement of the support. Thissmall angular displacement results in a correspondingly small componentof lateral displacement of the suspension point and a much smallervertical component of displacement; of the point. Thus the rate ofdisplacement of the suspension point in its effective vertical directionis an extremely small differential of the rate of turning movement ofthe adjustment screw. In this manner an angular displacement of theadjustment screw well within the capability and cognizance of anoperator will result in an almost infinitessimal displacement of thesuspension point relative to the fixture as a whole.

Still another object of the invention is to provide an adjusting meansof the character briefly outlined above in which the adjustment is apositive One and which will permit of no lost motion between the movableparts involved so that an adjustment may be made in either directionwithout involving errors due either to slack or other lost motionbetween the parts.

Still another object of the invention'is to provide an adjustingmechanism for suspension points in a fixture of this character which,once the adjustment has been made, will remain permanent so that thereis no shifting of the parts tending to destroy the adjustment.

The provision of a fixture of this character which has associatedtherewith means for providing accurate adjustment of its suspensionpoints within very fine limits, yet in which the adjusting means is notdelicate and which on the contrary is rugged and durable and thereforeis unlikely to get out of adjustment; one which may withstand suddenshocks without affecting the adjustment; one which is possessed of aminimum number of moving parts and which therefore is unlikely to getout of order; one which may be manufactured at a low cost by simplemachining operations, and one which otherwise is well adapted to performthe services required of it are further desirable'features that havebeen borne in mind in the production and development of the presentinvention.

In the accompanying two sheets of drawings forming part of this"-specification, several embodiments of this invention have beenportrayedpurely for illustrated purposes; In these drawings:

Fig. 1 is a top plan view of the fixture constructed in accordance withthe principles of the present invention and showing the same operativelyapplied to the rotary lap surface of the lapping machine.

Fig. 2 is a sectional view taken substantially along the line 2--2 ofFig. 1.

Fig. 3 is a perspective view of the fixture or article holder shown inFig. 1.

Fig. 4 is a perspective view similar to Fig. 1 showing another form offixture specifically designed for use in connection with the lapping ofarticles having angular surfaces such as optical prisms or the like.

Fig. 5 is a sectional view taken substantially along the plane indicatedby the line 5-5 of Fig. 4.

Fig. 6 is a sectional view similar to Fig. 5 showing a modified form ofadjusting means for the fixture suspension points.

Fig. 7 is a diagrammatic view illustrating certain trigonometricfunctions involved in connection with the suspension point adjustingmeans of any of the fixtures shown in Figs. 1 to 5 inclusive.

Fig. 8 is a diagrammatic view similar to Fig. 7 illustrating thetrigonometric functions involved in connection with the adjusting meansof Fig. 6.

Fig. 9 is a detail fragmentary view showing a slightly modified form ofadjusting means for the fixture suspension points.

In all of the above described views similar characters of reference areemployed to designate similar parts throughout.

In compliance with section 4888 of the Revised Statutes, severalpreferred forms of the invention have been shown in the drawings andwill be described herein, but it should be understood that the inventionis not limited to the specific disclosure made, and that the appendedclaims should be construed as broadly as the prior art will permit.

Referring now to the drawings in detail, Figs. 1 to 3 inclusiveillustrate an improved article holder or fixture 10 suitable for use inthe lapping of relatively thin articles such as piezoelectric crystalsso that the opposite surfaces of the crystals may be brought to a highdegree of flatness and. parallelism. In Figs. 4 to 6 inclusive amodified form of fixture 12 suitable for use in lapping an angular faceon the surface of a relative large article, as for example an opticalprism, has been illustrated.

The fixtures 10 and 12 are both suitable for use in connection withvarious forms of lapping machines and particularly the form of lappingmachine shown and de scribed in the above mentioned patent to E. I.Bullard, No. 2,565,590. Such a lapping machine has been fragmentarilyillustrated in Figs. 1 and 2 and only those portions of the machinenecessary to illustrate the particular use to which the present fixtureis put have been shown.

The particular lapping machine selected for illustration includes acircular lap plate 14 having an upper substantially flat annular lapsurface 16. The lap plate 14 is mounted for rotation about a verticalaxis so that the plane of the lap surface is substantially horizontal.Any suitable means (not shown) may be employed for continuously rotatingthe plate 14 about its vertical axis at a constant rate of movement.

The surface 16 of the lap plate 14 is adapted to be continuously dressedand maintained in its original flat condition by means of a conditioningring 18, the external diameter of which is greater than the radialdimension of the lap surface so that the ring may overhang either theinner or the outer edge of these surfaces. Such overhanging of theconditioning ring prevents the formation of shoulders or grooves in thelap surface which would render it unfit for the production of flat faceson the articles undergoing lapping. The ring 18 is preferably formed ofclose-grained cast iron such as Meehanite, and has a cross section suchas shown in Fig. 2. The ring 18 is held against circumferential shiftingmovement on the lap plate 14 but is free to rotate about its ownvertical axis. One means for thus restricting the movement of the ring18 is fully disclosed in the above mentioned Bullard patent and anothermeans is shown in the patent to Roshong, No. 2,627,144, dated Februray3, 1953, for Lapping Machine. It is deemed sufficient to state forillustrative purposes herein that the ring 18 is capable of rotationabout its fixed vertical axis under the influence of frictional contactwith the surface 16 of the lap plate 14. The lap surface 16 is adaptedto have applied thereto a suitable lapping compound in the form of anoil grit which is used to assist in grinding or lapping the articlespositioned on the lap surface. The means for applying and distributingsuch a lapping compound over the surface of the lapping plate has notbeen disclosed herein and reference may be had to the above mentionedBullard patent for a disclosure of such a means.

The improved article holder or fixture, as it is more generally termed,shown in Figs. 1 to 3 inclusive, is adapted to be loosely positionedwithin the conditioning ring 18 and this fixture involves in its generalorganization a generally triangular block 22 which may be formed ofsteel and it is provided with three inwardly bowed or curved sides 23which, in efiect, establish three radially extending diverging arms 24.The apices of the triangular block 22 are of appreciable extent and areconvex in configuration. The curvature thereof being substantially equalto the curvature of the inner periphery of the conditioning ring 18. Theblock 22 is provided with a substantially flat underneath surface 26(Fig. 2) to which the articles undergoing lapping may be secured. Forillustrative purposes a series of articles A in the form of quartzcrystals having extensive generally planar surfaces to begin with areshown as being wrung to the surface 26 by means of the application ofthe small amount of moisture which is placed on the contacting surfacesprior to application of the articles to the surface 26. When the articleis then applied to the underneath surface of the block 22, its facemakes intimate contact with the surface 26 so that the article is firmlyheld to the fixture by phenomena which are believed to be a combinationof molecular adhesion and atmospheric pressure.

The block 22 is provided with three spaced vertically extending bores28, each bore being provided in the block adjacent an apex of thegenerally triangular structure. Actually the bores 23 are in the form ofsplit clamping bores, there being a vertical split 34) provided at eachapex communicating with the adjacent bore 28. Each split 30 provides apair of opposed clamping arms 32 on opposite sides of the split and eachpair of arms is adapted to be drawn together to vary the size of thebore 28 by means of a pair of clamping screws 34 having enlarged heads36 seated in recesses 38 provided in one clamping arm 32 and havingshanks threadedly received in the other clamping arm.

Each bore 255 has disposed therein a cylindrical supporting rod 40, thevertical position, of which, within the bore, may be adjusted byloosening the clamping screws 34 to permit manual placement of thesupporting rods 40, after which the clamping screws may again betightened. The lower end of each supporting rod 40 is provided with asocket 42 therein designed to facilitate mounting of a suspensionelement in the form of a diamond rest 44 having a frusto-sphericalsurface 46 providing a suspension point for the fixture 10 as a whole,such suspension point being for a purpose that will be describedpresently. The diamond rest 44 may be in the form of a commercialdiamond, the surface of which is rounded, with the diamond being brazedin fixed position within the socket 42.

The three diamond rests 44 have a hardness which is greater than thesurface of the lap plate 14 or than the hardness of the floatingabrasive particles on the lap plate so that when these rests are incontact with the arm-1 s surface of the lap plateqthewear on' thediamondtests or upon the lap plate itself will be negligible. These suspensionpoints 46 are employed in connection with the fixture l inasmuch asthree rests will, when bearing against the lap surface 16, determineorestablish a plane for the underneath article-supporting surface 26.

An article such as a crystal A, when wrung to the supporting surface 26and lapped by this surface to completion, as determined by movement ofthe diamond rests 44 into coincidence with the plane of the lap surface,will be found to have a lapped .face parallel to the surface 26. It willbe appreciated that for best results, the surface 26 of the block 22must itself be planar. Otherwise its deviation from a plane vmay betransmitted to the face of an article being lapped. It must be assumedtherefore that the surface 26 is preferably fiat and smooth and it mustalso be assumed that the articles are preferably wrung onto this surfacewithout the inclusion of any g-rit or viscous fluid between the articleand the surface.

The initial positioning of the supporting rods v 40 within the bores 28constitutes, in, effect, a coarse adjustment for the diamond rests 44and means are provided whereby after such-positioning of the rods 40, anextremely fine adjustment of the position of these diamond rests may beattained, the means for effecting such a fine adjustment being bestillustrated inFigs. l and 2. At will be described presently, means areprovided forselectively imparting independent compound movements to thediamond rests involving both horizontal and vertical vincrements ofdisplacement. The ultimate plane established by such adjustment of theposition ofeach diamond rest is, of course, a function only of thevertical components of displacement applied to the rest and thehorizontal component of displacement imparted to the rest is onlyincidental to the attainment of the vertical displacement.

Referring now particularly to Figs. 1 and, 3, the block 22 is providedwith an inclined slot 50 adjacent each apex thereof which extendsupwardly from the underneath face of the block to a region not, farremoved from the upper face of the block where, it communicates with ahorizontally extending bore 52 which passes traversely through each arm24. The horizontal bores 52 intersect the vertical bo-res 28 as clearlyshown in Fig. 3. For convenience of manufacture, the .bore 52 may bedrilled in the block 22 prior to formation of the slots 50 andthereafter the slots may be, cut in the block by means of a band-sawwhich is ultimately guided into the bores 52 at which region theband-saw operation terminates.

The provision of the bores 52 and slots 50 previously referred toestablishes in effect an adjustable leg portion 54 at the outer end ofeach arm 24. Since each of the arcuate slots 50 involves a definiteremoval of metal during the machining operation and therefore ispossessed of appreciable width, each leg portion 54 is capable oflimited swinging, movement toward and away from the body of the block 22aboutan effective. horizontal axis such as has been designated by thedotted lines x-x in Fig. 1, the center of swinging movement beinglocated somewhat above the axis of the bore. 52. Each leg 54 effectivelyencompasses its respective rod 40 at least throughout a majorlongitudinal extent of the latter and therefore, as the leg is swunginwardly or outwardly as the case may be, tilting movement of the rod 40about the axis xx will result. Asa consequence the position of thediamond rest 44 will be shifted in an arcuate path such as has beendesignatedby the dotted arc yy of Fig. 2. Due to the inherent resilienceof the material from which the block 22 is formed, each leg willnormally be maintained spaced from the body of the block as shown inFig. 3 and, in order to adjustably control the angular disposition oftheleg 54', an' ad justing screw 56 passes through an opening 58provided 6 in one clamping arm 32, has its head countersunk intheopening and its shank threadedlyreceived in a socket 55,9 provided inthe main body of the block 22. Thus it will be seen that upontighteningof the screw 56 the leg 54 will be tilted about the axis x--xso as to cause the diamond rest 44 to sweep through the arcuate pathy-y.

The geometry of the movement of the diamond rest, ,upon such adjustmentof. the adjusting screw 56 is diagrammatically illustrated in Fig.7wherein a right angle triangle having sides a, b, c and angles A, B, Cand a rectangle having sides a, d, v and e are employed to illustratethe trigonometrical functions involved upon displacement of the diamondrest 44. In the schematic representation of Fig. 7, the distance hrepresents the distance from the axis x-x to the point 46 of contact ofthe diamond rest with the surface of the lap plate 14 or, in otherwords, the length .of the leg 54. This distance may be assumed to'befive inches. Assuming now that the pitch of the threads on the adjustingscrew 56 issuch that there are fifty threads to the inch, a singlecomplete turn of the adjusting screw in an effective direction willcause corresponding displacement of the leg 54 so that it assumes theposition represented by the side .0 of the triangle of the Fig. 7 andwherein the diamond rest is displaced laterally the distance a orapproximately .02 inch. The distances represented in Fig. 7 are onlyapproximate since the height of the adjusting screw 56 above theeffective contact point 46 of the diamond rest 44 has not been takeninto consideration and also since there may be a slight shifting of theefiective axis of swinging movement of the leg 54. The approximationsemployed are however sufficient to illustrate the principles involved.

The displacement of the diamond-rest 44 occasioned by a. single turn, ofthe adjusting screw 56 is represented by the dotted arc yy (see alsoFig. 3) and the diamond rest moves vfrom its initial position at 46 to anew position designated 46. This displacement involves the horizontalcomponent a and the vertical component v and it is this latter componentof motion that is of interest since it represents the verticaldisplacement of the diamond rest and the consequent alteration of theangularity of the plane common to all three of the diamond restsassociated with the fixture 10. The angle A of Fig. 7 is highlyexaggerated in order that the distance v maybe visualized in thediagram. Actually the angle A is on the order of lessthan a second ofangular extent.

It isobvious that in the diagram of Fig. 7

' c=b+d=h also: v=d

in order to 'find'the distance v in terms of the known quantities h anda, it is only ,necesary to find the distance d which is equal to it.

Solving for d geometrically:

b '2 2. b /h a a'=h /ha since h=2 inches and d=.02 inch It will beseenfrom the above solution that if one complete turn of the adjusting screw56 results in a .0004 inch vertical displacement of the'diamond rest 44,a small ad- 'justment' of the screw through one or two degrees only"will be capable of effecting a vertical adjustment of the rest which ismeasured in the millionths of an inch and which thus approximates thewave length of light.

to the plane of the surface 26. One or more articles may then be securedto the surface 26 by wringing them onto this surface in the mannerpreviously described. The fixture is then placed within the conditioningring 18 and the articles will bear against the lap surface with theweight of the fixture on the articles and serve to support the fixturein an elevated position so that the rests 44 will be elevated from thelap surface. The lapping operation is thus commenced and, as the lapplate rotates relative to the articles, the thickness of the articles isgradually reduced until such time as the diamond rests 44 move intocontact with the lap surface 16.

As the rests 44 closely approach the surface 16 they will move into thepath of the grit particles on the rotating surface and displace the samethus leaving visible tracks on the lap surface which will indicate tothe operator that lapping operations are approaching completion. Theprogress of lapping operations may thus be observed from the time thefirst rest closely approaches the plane of the lap surface through suchtime as the second rest and finally the third rest moves into closeproximity of the lap surface.

It will also be understood that no appreciable amount of lapping orwearing away of the diamond rests or of the lap surface itself will takeplace. In the first place, no efiiective lapping of the first twodiamond rests to descend upon the lap surface will occur and when thethird and last rest moves onto the plane of the lap surface, lappingoperations are complete and may be terminated. With careful placement ofthe articles on the surface 16 so as to place the composite center ofthe articles at or near the center of the triangular area defined by therests or apices of the triangle, the descent of the three rests may bealmost simultaneous so that the time interval between contact of thefirst rest and the last rest with the lap surface is of extremely shortor negligible duration. More important, however, is the fact that thehardness of the diamond rests relative to the hardness of the lapsurface, coupled with their relatively broad effective surface areas issuch that even with the full weight of the fixture being distributedamong the three rests, no noticeable wearing of the lap surface willtake place.

While the physical phenomena responsible for such lack of wear of thelap surface is not exactly understood, it is believed that the failureof the diamond material to yield to Wear results in actual descent ofthe plane face of the diamond rest into intimate contact with the lapsurface. In other words, the plane supporting face of the rest actuallymoves below the level of the grit particles and the particles are thuspushed aside so to speak so that there is an absence of grit particlesbetween the face of the diamond rest and the face of the lap surface.The rest thus slides on a clean lap surface and no wear of either therest or of the lap surface takes place. At the same time the presence ofcircular swaths where the three rests or stops come into contact withthe lap surface will indicate to the operator that lapping operationsare complete so that he may terminate the operation of the machine. Thusat no time during effective lapping operations on the articles are allthree diamond rests in contact with the lap surface.

In the lapping of crystals such as are shown at A, the articles willfirst be lapped on one side to provide a perfectly flat surface whichmay or may not be parallel with its opposite surface. The lapped surfacewill then be wrung on the surface 16 of the block 22 as described aboveand the unlapped surface then operated upon in accordance with the aboveprocedure to cause it to be lapped perfectly fiat and parallel with thefirst surface. Obviously, if the lap is not perfectly fiat, then thesurfaces of the article A likewise will not be fiat so that it isimperative for high precision work to maintain the surface of thelapping plate 14 as fiat as possible.

in the placement of crystals such as those shown at A in Fig. 1 on theunderneath surface 26 of the lapping plate 14, it has been found thatgenerally good lapping will take place'if the crystals are mounted onthe surface 26 so as to he completely within the triangular area boundedby a series of straight lines passing through the diamond rests 44.

Referring now to Figs. 4 and 5, a modified form of fixture suitable foruse in the lapping of optical prisms such as binocular prisms, or ofgauge blocks or the like has been shown. In this form of the invention,only the shape of the fixture body has been altered to accommodate theplacement of articles thereon while the diamond rests and theiradjusting means remain substantially the same as in the form of theinvention shown in Figs. 1 to 3 inclusive. To avoid needless repetitiousdescription, similar characters of reference have been applied to thecorresponding par-ts in the illustration of the two forms of theinvention and new reference characters applied only where significantdepartures take place.

Referring now specifically to Figs. 4 and 5, the fixture 12 is in theform of a block 60 of irregular configuration including a main bodyportion 62 provided with laterally projecting legs 64 and 66 whichextend from the body 62 in parallelism and in the same direction. Athird leg 68 on the opposite side of the body 62 projects laterally fromthe body. Split bores 28 are provided in the three legs 64, 66 and 68and receive therein supporting rods 49 identical with the supportingrods shown in connection with the fixture 10. Each supporting rodcarries a diamond rest 44 (Fig. 5) and is capable of tilting adjustmentin a manner identical with that previously described in the fixture 10.

The block 60 is provided with an inclined supporting surface 70 whichextends between the legs 64 and 66 and which is adapted to receivethereagaiust one face 72 of an article A such as the optical prism shownin dotted lines in Fig. 5. The prism A may have a surface '74 which itis desired to lap to a high degree of flatness so as to bring the sameinto coincidence with a plane which assumes a definite predeterminedfixed angle, as for example 60, with respect to the face 72 thereof.

The operation of the fixture 60is substantially the same as that of thefixture 10 shown in the previously described form of the invention. Thefixture 60 may be placed within a conditioning ring such as the ring 18of Fig. 2 and applied to the lap surface in the usual manner of lappingand it will be seen that when the three diamond rests 44 have all movedinto contact with the rotating surface of the lap plate, the desireddegree of prism angularity will have been applied to the face 74 of theprism or other article A.

Referring now to Fig. 6, a modified form of the adjusting means shown inconnection with the fixtures id and 60 previously described has beenillustrated. This adjusting means is capable of considerably fineradjustrnent than is the previously described adjusting means. Toillustrate the latter adjusting means, a fixture 100, which issubstantially identical with the fixture 6%) has been shown. Theadjusting means shown in Fig. 6 is similar in many respects to thepreviously illustrated adjusting means. In the drawings similarreference characters have been applied to corresponding parts to avoidneedless repetition of description.

The fixture is in the form of a block 62' similar to the block 62 andeach individual adjusting means is provided by the formation of avertical split bore 28 in which the supporting rod 40' is clamped bymeans of the clamping screws 34'. The curved slots 50, instead ofextending upwardly from the underneath face of the block, extenddownwardly from the upper face of the block to a region not far removedfrom the lower face of the block where they communicate with thehorizontally extending bores 52'. The adjusting screws 56 areconsequently located near the upper face of the block 100 while theeffective tilting axes xx' about which the swinging leg portions 54' areadapted to move are located adjacent the underneath surface of t heblock. The

geometry of the movement of each diamond rest 44',

upon adjustment of the adjusting screw 56 is diagrammaticallyillustrated in Fig. 8. In this figure the two right angle triangleshaving sides a, b, c and a", b" and respectively are employed toillustrate the trigonometric functions involved upon displacement of thediamond rest 44. It is not deemed necessary to enter into algebraicequations to measure the small vertical displacement v occasioned uponthe lateral displacement e of the diamond rest 44 and the diagram willvisually indicate that the comparative large displacement represented bythe side a when the adjusting screw 56' is turned throughout onecomplete turn will be accompanied by a much smaller displacement a" ofthe diamond rest. This latter displacement at results in an extremelysmall vertical displacement v. If it is assumed that the distance fromthe axes x'x to the plane of the adjusting screw 56' be 2 inches andthat the distance from the axis x-x to the point of contact 46' of thediamond rest 44 with the surface'of the lap plate be inches, thecorresponding diminution in the value of the vertical displacement vfrom the value of the vertical displacement v shown in Fig. 7 will be A;of this former value. The displacement v' may therefore be even lessthan the wave length of light.

In the forms of the invention previously described, the adjusting screws56 and 56 are shown as having their end regions threadedly received withthe main body portion of the article holder with the shanks passingloosely through the leg portion. Thus upon turning of the adjustingscrew in one direction the leg portion will be drawn inwardly of thefixture to decrease the width of the slot during movement of the diamondrest in its arcuate path. In Fig. 9 the adjusting screw 56a is shown asbeing threadedly received through the leg portion 54a with its endbearing against the remote side of the arcuate. slot 50a. It is obviousthat upon turning movement of the adjusting screw 56a in one direction,the leg portion 54a will be moved away from the main body portion of theblock so as to cause the diamond rest 44a to be swung outwardly awayfrom the block in an arcuate path.

The invention is not to be limited to the exact arrangement of partsshown in the accompanyingdrawings or described in this specification,since various changes in the detail of construction may be resorted towithout departing from the spirit of the invention. For example, whilethe invention has been illustrated herein in connection with aconditioning ring such as the conditioning ring 18 which is restrainedagainst revolution about the lap surface, any of the fixtures shownherein may be adapted for application to the lap surface and forrestraint thereon independently of whether any conditioning ring is oris not employed. For this purpose a vertical bore such as the bore 20 ofFigs. 1 to inclusive, or the bore 20' shown in Fig. 6 may extendcentrally through the respective fixture for reception therein acentering pin (not shown) associated with the lapping machine framework,and by means of which the fixture is restrained against revolution aboutthe. axis of the lap while at the same time permitting rotating of thefixture upon the lap. Only in so far as the invention has been pointedout in the accompanying claims, is the same to be limited.

What is claimed is:

1. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder comprising asolid block of metal provided with a surface to which an article to belapped is adapted to be afiixed and by means of which the article isapplied to the lap surface with the weight of the holder supported uponthe article, three limit stop members mounted on the holder and designedfor ultimate contact with the lap surface to thus determine the extentof lapping operations performed upon the article by providing athree-point support for the holder and article aifixed thereto,adjusting means for one of said limit stop members to vary the positionthereof, said means comprising a supporting leg capable of swingingmovement relative to the body of the holder about a horizontal axis,said adjustable limit stop member being carried at the free end of saidleg, and means for adjusting the angular position of said leg relativeto the body of the fixture.

2. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder having asurface to which an article is adapted to be atfixed and by means ofwhich the article is applied to the lap surface with the weight of theholder supported upon the article, a limit stop member mounted on theholder and designed for ultimate contact with the lap surface to thusdetermine the extent of lapping operations performed upon the article byproviding a support for the holder and article afiixed thereto, saidlimit stop member being movable in an arcuate path relative to the bodyof the holder about a horizontal axis whereby said member may have bothhorizontal and vertical components of movement, and means for adjustingposition of said stop member in its arcuate path of movement.

3. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder including abody portion provided with a surface to which an article to be lapped isadapted to be aflixed and by means of which the article is applied tothe lap surface with the weight of the holder supported upon thearticle, three limit stop members mounted on the holder and designed forultimate contact with the lap surface to thus determine the extent oflapping operations performed upon the article by providing a three-pointsupport for the holder and article afiixed thereto, a supporting leg forone of said limit stop members, said leg being integral with said bodyportion and oscillatable relative to the latter about a horizontal axis,said limit stop member being carried at the free end of the supportingleg, and means for adjusting the angular position of said leg relativeto the body portion of the article holder whereby the vertical componentof movement of the limit stop member will be a function of the sine ofthe angle of displacement of the limit stop member.

4. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder including abody portion, means on said body portion for supporting an article infixed position whereby the article may be applied to said movable lapwith the weight of the holder resting upon the article, three limit stopmembers mounted on the holder and designed for ultimate contact with thelap to thus determine the extent of lapping operations performed uponthe article by providing a three-point support for the holder andarticle, and a supporting leg for one of said limit stop membersoscillatable relative to the body portion of the holder about ahorizontal axis, said latter limit stop member being carried at the freeend of said leg, and an adjusting screw extending through said leg andthreadedly received in said body portion for adjusting the angularposition of the leg.

, 5. In a machine for lapping a face on an article, means providing alap surface, an article holder, means establishing relative movementbetween said article holder and lap surface, said article holderincluding a body portion, and a leg portion carried by said body portionand oscillatable relative thereto about a horizontal axis, means forsecuring an article to the holder for application to the lap surface ofthe machine with the weight of the holder supported upon the article, alimit stop member mounted on the free end of said leg portion anddesigned for ultimate contact with the lap surface to thus determine theextent of lapping operations performed upon the article by providing asupport for the holder, and means extending through one of saidmembersand threadedly received in the other member for adjusting the angularposition of the leg portion relative to the body portion.

6. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder including abody portion,

and a leg portion carried by said body portion and oscillatable relativethereto about a horizontal axis, means for securing an article to theholder for application to the lap surface of the machine with the weightof the holder supported upon the article, a limit stop member mounted onthe free end of said leg portion and designed for ultimate contact withthe lap surface to thus determine the extent of lapping operationsperformed upon the article by providing a support for the holder, and anadjusting screw extending loosely through one of said members andthreadedly received in the other member for adjusting the position ofsaid leg portion relative to said body portion.

7. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder including abody portion, and a leg portion carried by said body portion andoscillatable relative thereto about a horizontal axis, means forsecuring an article to the holder for application to the lap surface ofthe machine with the weight of the holder supported upon the article, alimit stop member mounted on the free end of said leg portion anddesigned for ultimate contact with the lap surface to thus determine theextent of lapping operations performed upon the article by providing asupport for the holder, and an adjusting screw extending through andthreadedly received in said leg portion and bearing against said'bodyportion for adjusting the position of the leg portion relative to thebody portion.

8. In a machine for lapping aface on an article, means providing a lapsurface, an article holder, means establishing relative movementbetweensaid article holder and lap surface, said article holder, a surface towhich an article is ada'ptedtobe afiixed and by means of which thearticle is applied to the lap surface with the weight of the holdersupported upon the article, said holder comprising a solid block ofmetal having a relatively deep slot formed therein dividing the holderinto a main body portion and a leg portion capable of bodily swingingmovement relative to the body portion about a horizontal axis, a limitstop member carried at the free end of said leg portion, and means foradjusting the angular position of said leg portion relative to said bodyportion.

9. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder having asurface to which an article is adapted to be affixed and by means ofwhich the article is applied to the lap surface with the weight of theholder supported upon the article, said holder comprising a solid blockof metal having a relatively deep slot formed therein dividing theholder into a main body portion and a leg portion capable of bodilyswinging movement relative to the body portion about a horizontal axis,a limit stop member carried at the free end of said leg portion, andmeans for adjusting the angular position of said leg portion relative tosaid body portion, said adjusting means comprising an adjustable screwpassing through said leg portion and threadedly received in said bodyportion.

10. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder having asurface to which an article is adapted to be affixed and by means ofwhich the article is applied to the lap surface with the weight of theholder supported upon the article, said holder comprising a solid blockof metal having a relatively deep slot formed therein dividing theholder into a main body portion and a leg portion capable of bodilyswinging movement relative to the body portion about a horizontal axis,a limit stop member carried at the free end of said leg portion, andmeans for adjusting the angular position of said leg portion relative tosaid body portion, said adjusting means comprisingan adjusting screwpassing through and threadedly received in said leg portion and bearingagainst said body portion.

1]. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder having asurface to which an article is adapted to be aflixed and by means ofwhich the article is applied to the lap surface with the weight of theholder supported upon the article, said holder comprising a solid blockof metal having a relatively deep slot formed therein dividing theholder into a main body portion and a leg portion capable of bodilyswinging movement relative to the body portion about a horizontal axis,a limit stop member carried at the free end of said leg portion, andmeans for adjusting the angular position of said leg portion relative tosaid body portion, said adjusting means comprising an adjusting screwpassing through and threadedly received in one of said portions andbearing against the other portion.

12. In a machine for lapping a face on an article, means providing a lapsurface, an article holder, means establishing relative movement betweensaid article holder and lap surface, said article holder havinga surfaceto which an article is adapted to be affixed and by means of which thearticle is applied to the lap surface with the weight of the holdersupported upon the article, said holder comprisinga solid block of metalhaving a relatively deep slot formed therein'dividing the holder into amain body portion and a leg portion capable of bodily swinging movementrelative to the body portion about a horizontal axis, there being asubstantially vertically extending bore formed in said leg portion, asupporting rod adjustably secured in said bore and having one endthereof projecting outwardly thereof, a limit stop member mounted on theprojecting end of said supporting rod, and means for adjusting theangular position of said leg portion relative to said body portion.

References Cited in the file of this patent UNITED STATES PATENTS338,322 Waters Mar. 23, 1886 1,192,416 Graves July 25, 1916 2,363,544Mogey Nov. 28, 1944 2,397,860 Hodgdon Apr. 2, 1946 2,412,306 Stoll Dec.10, 1946 2,565,590 Bullard Aug. 28, 1951 2,627,144 Roshong Feb. 3, 19532,722,089 Boettcher Nov. 1, 1955

